1. Field of the Invention
This invention relates to a ceramic engine using fuel alcohol.
2. Description of the Prior Art
A conventional heat insulating engine in which a ceramic liner head having cylinder liner upper portions is fitted in a cylinder head is disclosed in, for example, Japanese Patent Laid-open No. 122765/1984.
The conventional 2-cycle engines include a uni-flow scavenging type engine adapted to carry out an asymmetric scavenging operation and capable of carrying out a post-suction operation, in which engine exhaust valves are provided in the exhaust ports formed in a cylinder head, or exhaust ports are provided in the whole circumferences of cylinder liner upper portions, with scavenging ports provided in the whole circumferences of cylinder liner lower portions, whereby the prevention of a mixed flow of the scavenging air and exhaust gas and the improvement of the scavenging efficiency and suction efficiency are effected.
Constructing a 2-cycle heat insulating engine so that the crank chambers function as compressors is generally carried out.
The environmental pollution due to the exhaust gas from an engine has given rise to public discussion, and an alcohol engine has recently attracted public attention. With an alcohol engine, the carbon dioxide and carbide contents of the exhaust gas are very low as compared with those from the engines using gasoline and light oil as fuels.
However, in a 2-cycle engine using alcohol as a fuel, the ignitability of the fuel is inferior. Namely, alcohol requires larger amount of latent heat for the gasification thereof as compared with gasoline and light oil. For example, gasoline requires a latent heat of 0.7% of its heating value, while alcohol requires a latent heat of 5% of its heating value. Namely, alcohol has a property of being difficult to be gasified. Moreover, alcohol injected from the alcohol injectors, i.e. fuel injection nozzles into the air in the suction passages lowers the temperature of suction air, and, when the alcohol mixed with the suction air in this condition are introduced into combustion chambers, the ignition condition of the gaseous mixture is necessarily deteriorated.
Therefore, if a heat insulating engine using alcohol as a fuel is constructed so that the temperature of an engine body as a whole increases to a high level to enable the heat to be taken out from the high-temperature wall surface thereof and the gasification latent heat to be supplied to the sucked alcohol for the gasification thereof, the gasification of the alcohol is promoted, and an excellent gaseous mixture is produced.
However, when the temperature of the engine as a whole is increased to a high level, oil cannot to stored in the crank cases. In such a 2-cycle heat insulating engine, various measures are usually taken for a lubricating system, by which a rotary sliding portion of a crank journal of a crankshaft and those of the larger- and smaller-diameter portions of connecting rods are lubricated, for eliminating this inconvenience. When the sliding portions are heated to a high temperature during the sliding movements of the piston rings and cylinder liners, seizure occurs. Therefore, this type of engine has a problem of how to construct a lubricating system for these sliding portions.
In an engine of a 2-cycle operation, the air suction/exhaust is carried out as follows. When the exhaust valves are opened to discharge the exhaust gas via the exhaust ports, pressure waves, i.e. pulse waves occur in the cylinders, so that the exhaust gas is thereby forced out. Consequently, fresh air enters the cylinder lower portions and flows into vacuum zones occurring on the rear side of the exhaust gas. Since the cylinder lower portions are heated to not so high a temperature as compared with the cylinder head, the fresh air is not much influenced by the temperature of the inner surfaces thereof. This enables, especially, a heat insulating engine to be operated advantageously, i.e., when a 2-cycle operation is carried out therein to suck fresh air via the cylinder lower portions, the flow rate of the scavenging air or suction air does not decrease.